gospacex, this is a general comment and not aimed specifically at you.

I keep seeing this statement ("Unlike LOX one, which can only burn") and others like it all over the place, and while I know it's a fine distinction, it is *not* true that LOX (oxygen) burns. Oxygen does not burn. It is not a fuel. It is an oxidizer. Fuel cannot burn without the presence of an oxidizer to support combustion, and oxygen, in this case, is that oxidizer. In fact the term "burn" is common speech for combustion and actually means "oxidizing" the fuel, such as hydrogen, kerosene, RP1, gasoline, paper, wood, etc. Combustion requires at least 2 things, a fuel to burn and an oxidizer to support the burn. The fuel burns, the oxidizer does not. It molecularly combines with the fuel to create the "oxidation process", called combustion. There are other oxidizers as well besides oxygen. All of them are oxidizers, not fuel, and none of them "burn". They all support combustion and allow the fuel, whatever it is, to combust, or burn. Chemistry 101.

Likewise it is incorrect to describe LOX as explosive. It is not. What is generally being referred to when this term is misapplied is that the ET, as a "pressure vessel" can rupture under the high internal pressure. That does not take a spark or ignition or combustion of any kind, just a structural imperfection in a weld or some other less than satisfactory "mechanical" property of the structure of the tank. Granted, the end result is often the same, especially if the rupture also releases large quantities of fuel to mix with the released oxygen (Challenger) which then supports the "fuel" exploding, but the oxygen did not explode, the structural pressure vessel ruptured.

Can we use the correct terminology please?

« Last Edit: 03/23/2009 10:58 AM by clongton »

Logged

Chuck - DIRECT co-founderI started my career on the Saturn-V F-1A engine

From where I stand, gospacex did use the correct term - a "LOX one" as in engine means it has a fuel in addition to LOX. If the two are not well mixed, no detonation is possible. Any by definition, keeping both fuel and oxidizer (in this case LOX) in separate tanks prevents them from mixing. I don't see that statement as implying it's LOX itself that burns.

From where I stand, gospacex did use the correct term - a "LOX one" as in engine means it has a fuel in addition to LOX. If the two are not well mixed, no detonation is possible. Any by definition, keeping both fuel and oxidizer (in this case LOX) in separate tanks prevents them from mixing. I don't see that statement as implying it's LOX itself that burns.

Oxygen does *not* burn.

Logged

Chuck - DIRECT co-founderI started my career on the Saturn-V F-1A engine

Google "LOX one" and you won't get the reference you refer to. You will gets hundreds of hits something like this:"Lyrics for One Two Three Four by The Lox. Album DJ Clue "So that's just another example of what I was trying to get at and afaik, that term isn't found in a technical manual or reputable dictionary either.

My post was in regards to the use of proper terminology, especially when discussing things of a technical nature. Introducing coloqual terms into a technical discussion is not appropriate given the nature of the subjects. It can and has led to misinterpretations.

I have seen professors ask students to leave the class when they did that, and my request was for folks to take pains to use the proper terminology and use it correctly. This isn't a rap around a campfire. Perhaps I'm old school, but I like to know that the terms I see used in a technical discussion are actually there in the dictionary and continue to mean what they have always meant.

But that's just me.

Logged

Chuck - DIRECT co-founderI started my career on the Saturn-V F-1A engine

I have seen professors ask students to leave the class when they did that, and my request was for folks to take pains to use the proper terminology and use it correctly. This isn't a rap around a campfire. Perhaps I'm old school, but I like to know that the terms I see used in a technical discussion are actually there in the dictionary and continue to mean what they have always meant.

Thats fine. I take your meaning and I understood what you were getting at in the first place. That wasnt the point, and is why I started by saying it was a general comment, not specific to you.

I see so much these days of folks allowing their English to slip into word usages that are not correct, being linguistically lazy. Folks like me who speak English as a native language often forget that English is *THE* most difficult language on earth to learn as a foreign language. Thats why it is so important, especially in a technical conversation, to take pains to use the correct terminology and to apply it correctly. There are many people on this forum from non-English speaking nations and what they are reading here is a foreign language to them. We English-speakers too often forget that. When we allow ourselves to become casual with how we use our terms, it can make it difficult for them. Hell, it is even difficult for English speakers sometimes to figure out what someone has said.

So like I said, my point was to encourage folks to think about what they want to say before they post it, not only so that it is conceived correctly, but also that it is spoken correctly. Set your language bar high and then reach for it. Thats all I was getting at. I used burning oxygen as the example, because I see that incorrect usage so often.

« Last Edit: 03/23/2009 12:44 PM by clongton »

Logged

Chuck - DIRECT co-founderI started my career on the Saturn-V F-1A engine

Another thing that needs to be pointed out: solids can only ignite under a very hot ignition source to begin with. I don't think even a typical match already burning would do it. Please correct my impression if I'm wrong.

Logged

If I like something on NSF, it's probably because I know it to be accurate. Every once in a while, it's just something I agree with. Facts generally receive the former.

"HTP Explosion Hazard: The action of detonators on HTP has shown that it is possible to partially explode 90% material if it closely confined, and under severe conditions of shock and confinement it has been known to detonate at 80%-85% strength."

100% HTP has the same freezing point as water, 0 C. So if you can keep large volumes of water from freezing, you can do the same with HTP.

If anybody wants a scan of various paper and manuals relating to HTP, email me and I will send them to you.

Logged

Akin's Laws of Spacecraft Design #1: Engineering is done with numbers. Analysis without numbers is only an opinion.

I don't have it on hand, but the program I use gives a density of 1.2284 kg/L, exhaust speed of 3242 m/s, impulse density of 3982 Ns/L and a mixture ratio of 7.8. This is better than O2/RP-1, but worse than HTP/RP-1 as a first stage propellant.

By the way, the highest impulse density propellant I know of is F2/NH3 (liquid fluorine and ammonia). F2 has a density of 1.505 kg/L and NH3 0.676 kg/L. With such high density propellants, at a MR of 3.4 you get dp = 1.1770 kg/L, ve = 4115 m/s and Id = 4843 Ns/L, 32% better than O2/RP-1 if you don't mind a hydrofluoric acid exhaust. :-) I've also added data for F2/H2 which has an Id more twice that of O2/H2 with a better ve.

Any other propellant combinations the readers here would like me to try?

« Last Edit: 03/24/2009 06:08 AM by Steven Pietrobon »

Logged

Akin's Laws of Spacecraft Design #1: Engineering is done with numbers. Analysis without numbers is only an opinion.

There's occasionally talk of being able to shut down a solid without destroying it by jettisoning the nozzle with ordnance, but that joint itself would be unsafe.

Is this charge down a significant length of the SRB ? Does this zipper cause it to break apart, and does this propellant continue to burn as it falls to splashdown ?

What the heck happens if they abort Ares I before, or shortly after clearing the tower ? Would you have a mass of solid rocket fuel burning on/near the pad til it was exhausted ? Even if the SRB was zipped open ?

I've also heard of a concept of blowing off the top of an "out of control" solid... But the fact is that the nature are solids such that they don't go "out of control" in a standard sense. They quickly transistion to and overpressure situation and blowup. So while NASA claims the RSRBs don't blowup... I'm having trouble believing them.